Selective defect in gonadotrophin secretion in patients with autonomic failure

We studied the neuroendocrine effects of a condition associated with abnormal hypothalamic amines. Hypothalamo-anterior pituitary function was assessed in five male subjects with autonomic failure (AF) and in five age and sex-matched controls. All subjects showed normal gonadotrophin and TSH responses to GnRH and TRH, respectively. In control subjects, intravenous infusion of naloxone caused a significant rise in overall LH concentrations as well as increased frequency and amplitude of LH pulses. In contrast, in AF subjects naloxone did not alter LH concentrations or increase LH pulse frequency. Naloxone also caused an increase in neurosecretory GH pulses not only in AF subjects but also in the controls. These results suggest that in man, ascending catecholamine pathways are important in the control of gonadotrophin secretion. The markedly different response of GH to an opioid antagonist in elderly subjects should be further investigated.